1,865 research outputs found
Phase angle in the Cu/polyimide/alumina system
No full textA linear elastic fracture mechanics analysis was extended to determining the phase angle of an interface crack between Cu/polyimide in the elasto-plastic peel test of Cu/polyimide/alumina structure. Then, the fracture mechanics solutions of the phase angle for the thin film/substrate structure were extended to the Cu/polyimide/alumina structure by assuming the path independence of J-integral, which turned out to be quite true with or without polyimide. The peel crack propagation occurred under the mixed mode in all cases with phase angles virtually independent of the metal film thickness, which is in good agreement with our earlier work [1] showing nearly constant interfacial fracture energy with the film thickness. The presence of the polyimide layer increased the mode mixity shifting the phase angle by 11-12 degrees, which indicates that ignoring the polyimide interlayer may result in some underestimation of the real phase angle of multilayer films under the peel test. (C) 1999 Elsevier Science S.A. All rights reserved
Combined analysis of moisture diffusion with interface fracture mechanics on the interface delamination in the plastic IC packages during reflow soldering
No full text
Enhanced thermoelectric power factor in Yb1−xScxAl2 alloys using chemical pressure tuning of the Yb valence
No full textWe have investigated the influence of Sc substitution on the transport and magnetic properties of YbAl2, a well-known intermediate valence compound. Sc substitution provides a chemical pressure that decreases the lattice constant and thereby alters the Yb valence as a function of composition and temperature. We observe a strong correlation between the Seebeck coefficient and the ratio of trivalent to divalent Yb in these compounds, as determined from magnetic susceptibility measurements. This correlation indicates that the largest absolute value of the Seebeck coefficient is achieved when the average Yb valence is near 2.5 (the ratio of divalent to trivalent Yb is 1: 1). It is shown that Sc concentration can be used as a means to tune both the magnitude of the maximum of the Seebeck coefficient and the temperature at which this absolute maximum occurs, improving the prospects of the use of these materials in cryogenic Peltier coolers. (C) 2013 AIP Publishing LLC.11108sciescopu
Characterization of extracellular α-galactosidase produced by Streptomyces sp. YB-4
No full textA strain YB-4 producing the extracellular α-galactosidase was isolated from soil, and has been identified as Streptomyces sp. on the basis of its cultural, morphological and physiological properties. The partially purified α-galactosidase was most active on paranitrophenyl-α -D-galactopyranoside at pH 6.0 and 60°C. The enzyme retained 90% of its maximum activity between pH 4.0 and pH 10.0 after pre-incubation for 1 h. The enzyme was able to hydrolyze oligomeric substrates such as melibiose, raffinose and stachyose to liberate galactose residue, indicating that the α-galactosidase of Steptomyces sp. YB-4 hydrolyzed α-1,6 linkage.open
Towards the tumble resistant microlight
No full textThe tumble mode is a pitching departure from controlled flight which leads to a pitch autorotation that is generally unrecoverable – resulting in vertical ground impact, usually preceded by in-flight breakup (the mechanism for which, surprisingly, can sometimes prevent loss of life). This was identified in work led by the British Microlight Aircraft Association beginning in 1997 as a response to a number of fatal accidents in Rogallo winged microlight aeroplanes, although the tumble is also known to occur to hang-gliders. This paper explains how this class of aeroplane is controlled, and how it has been found that they can enter the tumble mode. The mechanism by which the tumble can be entered is described. This has led to work showing how flight testing can be used to establish and demonstrate resistance to tumble entry – particularly important with increasing number of very high performance flexwings. These flight tests will be explained, together with the significance of the results. Recent accident investigation work has also shown a new mechanism of tumble entry, through partial failure of the A-frame structure and the pitch-trimmer mechanism. Also described is a possible relevance to well known historical accidents to flying wing aeroplanes– specifically the YB-49 and dH-108, and discovered data on the characteristics of the BKB-1flying wing glider; are also described
Characterization of the extracellular β-galactosidase produced from Streptomyces sp. YB-9
No full textA strain YB-9 was isolated from soil as a producer of the extracellular beta-D-galactosidase, which catalyzes the hydrolysis of lactose. The strain YB-9 was identified as Streptomyces sp. on the basis of its cultural, morphological and physiological properties.open
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